The present disclosure relates to a catalyst, a method of forming the catalyst, and applications of the catalyst, and more particularly to a catalyst useful for oxidizing carbon monoxide selectively in a hydrogen rich environment.
Exhaust gases, such as those produced by a partial oxidation, autothermal, or steam reforming reaction of hydrocarbons, to produce a hydrogen (H2) rich reformate, are passed through a catalytic converter to remove undesirable components such as carbon monoxide (CO). Significant amounts of CO, which serve to diminish the functionality of precious metals found in components downstream of the reforming reactor, for example, precious metals found in a proton-electrolytic membrane fuel cell anode, are present in the H2-rich reformate. Conventional oxidation catalysts (e.g., platinum (Pt), rhodium (Rh), or iridium (Ir)) are currently used for CO removal. However, these precious metal containing catalysts are not selective to CO oxidation, and the oxidation of hydrogen by these catalysts is also significant. Therefore, in order to maximize CO oxidation activity, while minimizing H2 oxidation activity, most existing CO preferential oxidation catalysts operate over a very narrow temperature range in which the CO oxidation activity is relatively high compared to the H2 oxidation activity, although some H2 oxidation occurs. The use of such a narrow temperature range presents a difficult process control situation. Thus there remains a need in the art for a catalyst that is preferentially selective to CO over H2, and which can be used over a wide temperature range, thus eliminating the need for a sophisticated process control system, and thereby resulting in a simpler, more efficient, and less expensive fuel processing system.